Electrical Final

Some electric motors have two sets of field windings wound in opposite directions so that the

motor can be operated in either direction.

One purpose of a growler test is to determine the presence of

a shorted armature

Electric wire terminals for most aircraft applications must be what type?

Ring

What is the principal advantage of the series-wound DC motor

High starting torque

If a generator is equipped with a vibrator-type voltage regulator, the actual time the voltage regulator points remain open

depends on the load carried by the generator.

What is a cause of generator brush arcing?

Low spring tension

What is required when operating two aircraft AC generators in parallel?

Frequency and voltage must both be equal.

The starting current of a series-wound DC motor, in passing through both the field and armature windings, produces a

high starting torque

Which motor would be most likely to have an armature brake?

Landing light retraction motor

The method most often used in overcoming the effect of armature reaction is through the use of

interpoles

The only practical method of maintaining a constant voltage output from an aircraft generator under varying conditions of speed and load is to vary the

strength of the magnetic field.

The pole pieces or shoes used in a DC generator are a part of the

field assembly

How many cycles of AC voltage are produced in a six-pole alternator of the revolvingfield type for each revolution of the rotor?

Three

If the reverse current cutout relay contact points fail to open after the generator output has dropped below battery potential, current will flow through the generator armature

opposite the normal direction and through the shunt field in the normal direction.

How does the magnetic brake used to stop rotation of an electric motor armature operate?

A friction brake is applied by a spring and released by a magnet

In a generator, what eliminates any possible sparking to the brush guides caused by the movement of the brushes within the holder?

The brush pigtail

A series-wound DC electric motor will normally require

more current at low RPM than at high RPM.

The type of electric wire terminals used for most aircraft applications, in addition to providing good current carrying capabilities, are designed primarily

to prevent circuit failure due to terminal disconnection

Aluminum wire must be stripped very carefully because

individual strands will break easily after being nicked.

The commutator of a generator

changes alternating current produced in the armature into direct current as it is taken from the armature.

An ammeter in a battery charging system is for the purpose of indicating the

rate of current used to charge the battery.

Which of the following is not one of the purposes of interpoles in a generator?

Reduce field strength

To test generator or motor armature windings for opens,

place armature in a growler and connect a 110V test light on adjacent segments; light should light.

What is the color and orientation of the position lights for navigation on civil airplanes?

Left side, red; right side, green; rear aft, white

To what depth is the mica insulation between the commutator bars of a DC generator undercut?

Equal to the width of the mica

A voltage regulator controls generator output by

varying current flow to generator field coil.

Which type of DC generator is not used as an airplane generator?

Series wound

During ground operation, aircraft generator cooling is usually accomplished by

an integral fan

What does a rectifier do?

Changes alternating current into direct current.

Which of the following are the major parts of a DC motor?

Armature assembly, field assembly, brush assembly, and end frame

Which of the following statements is true?

In the series motor, the field windings, consisting of relatively few turns of heavy wire, are connected in series with the armature winding.

What is the appropriate method for installing pre-insulated terminal lugs and splices to electric wires?

Using a crimping tool to secure the terminal lug.

Which of the following factors must be taken into consideration when determining the wire size to use for an aircraft installation?

Allowable power loss, permissible voltage drop, current carrying capability of the conductor, type of load.

How should the splices be arranged if several are to be located in an electrical wire bundle?

Staggered along the length of the bundle.

What is the minimum bend radius for an electrical wire bundle?

Ten times the outside diameter of the bundle

When approved, splices may be used to repair manufactured harnesses or installed wiring. The maximum number of splices permitted between any two connectors is

one

Electrical connectors used in the aircraft assemblies should meet which of the following specifications?

Military Specifications (MS).

The most common method of attaching a pin or socket to an individual wire in an MS electrical connector is by

crimping

The pin section of an AN/MS connector is normally installed on

the ground side of a circuit.

The voltage output of an alternator may be regulated by controlling the

voltage output of the dc exciter.

If several long lengths of electrical cable are to be installed in rigid conduit, the possibility of damage to the cable as it is pulled through the conduit will be reduced by

dusting the cable with powdered soapstone.

Grounding is electrically connecting a conductive object to the primary structure. One purpose of grounding is to

prevent development of radio frequency potentials.

Aircraft fuse capacity is rated in

amperes

When adding a rheostat to a light circuit to control the light intensity, it should be connected in

series with the light.

Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ

guarded switches

If one switch is used to control all navigation lights, the lights are most likely connected

parallel to each other and in series with the switch.

Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be

a shorting hazard

Electric wiring installed in aircraft without special enclosing means (open wiring) offers the advantages of ease of installation, simple maintenance, and reduced weight. When bundling open wiring, the bundles should

be limited as to the number of cables to minimize damage from a single electrical fault.

During inspection of the terminal strips of an aircraft electrical system, it should be determined that

the terminal studs are anchored against rotation.

What protection to wires and cables does conduit provide when used in aircraft installations?

Mechanical

Which of the following should be accomplished in the installation of aircraft wiring?

Locate the bundle above flammable fluid lines and securely clamp to structure.

The nominal rating of electrical switches refers to continuous

current rating with the contacts closed.

Aircraft electrical junction boxes located in a fire zone are usually constructed of

stainless steel

The primary considerations when selecting electric cable size are

current-carrying capacity and allowable voltage drop

The navigation lights of some aircraft consist of a single circuit controlled by a single switch which has an ON position and an OFF position, with no additional positions possible. This switch is referred to as a

single-pole, single-throw (SPST), two-position switch

Electric circuits are protected from overheating by

fuses

Which of the following copper electrical cable sizes should be selected to replace a No. 6 aluminum electrical cable?

No. 6

In installations where the ammeter is in the generator or alternator lead, and the regulator system does not limit the maximum current that the generator or alternator can deliver, the ammeter can be redlined at what percent of the generator or alternator rating?

100

Which statement relating to electric wiring is true?

When attaching a terminal to the end of an electric cable, it should be determined that the strength of the cable-to-terminal joint is at least equal to the tensile strength of the cable itself.

What kind of switch should the aviation mechanic install in a single wire circuit that requires the switch to be manually held in the ON position?

Single-pole, single-throw (SPST), two-position normally open (NO).

A circuit breaker is installed in an aircraft electrical system primarily to protect the

circuit and should be located as close to the source as possible.

A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be used in

heavy power circuits.

If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic should

use a special moisture-proof type

Which of the following are considered circuit-protective devices that are used in aircraft electrical systems?

Circuit breakers, fuses, and current limiters.

If a wire is installed so that it comes in contact with some moving parts, what protection should be given the wire?

Pass through conduit

In the American Wire Gauge (AWG) system of numbers used to designate electrical wire sizes, the number assigned to a size is related to its

cross-sectional area

How should a voltmeter be connected?

In parallel with the load

What is the voltage drop for a No. 18 copper wire 50 feet long to carry 12.5 amperes, continuous operation? Use the formula: VD = RLA

VD = Voltage drop

R = Resistance per ft = .00644

L = Length of wire

A = Amperes

4V

What is the purpose of the selection of derated switches for known continuous load current applications?

To obtain reasonable switch efficiency and service life.

What is the advantage of a circuit breaker when compared to a fuse?

It is resettable and reusable

What is the advantage of a current limiter?

It will take overload for a short period.

What should be used to protect wires from chafing when they must pass through bulkheads, firewalls, ribs, etc.?

Suitable grommet.

In aircraft electrical systems, automatic reset circuit breakers

should not be used as circuit protective devices

A certain switch is described as a single-pole, double-throw (SPDT) switch. The throw of a switch indicates the number of

circuits each pole can complete through the switch.

When considering an alteration, the criteria upon which the selection of electric cable size should be based are

current-carrying capacity and allowable voltage drop

What is an important factor in selecting aircraft fuses?

Capacity matches the needs of the circuit.

The circuit breaker in the instrument lighting system protects the

wiring from too much current

One advantage of using AC electrical power in aircraft is

greater ease in stepping the voltage up or down

Why are the iron cores of most induction coils laminated?

To reduce the effects of eddy currents

Certain transport aircraft use AC electrical power for all normal operation and battery furnished DC electrical power for standby emergency use. In aircraft of this type that operate no DC generators, the batteries are kept charged by

inverters which use the aircraft's AC generators as a source of power

If the positive field lead between a generator and a generator control panel breaks and is shorted while the engine is running, a voltmeter connected to generator output would indicate

residual voltage

What is a method used for restoring generator field residual magnetism?

Flash the fields

The major advantages of alternating current (AC) over direct current (DC) is the fact that its current and voltage can easily be increased or decreased

by means of a transformer

Which of the following must be accomplished when installing an anticollision light?

Install a switch independent of the position light switch.

The inductor-type inverter output voltage is controlled by the

dc stator field current

When using an ohmmeter to check the continuity of a generator field coil, the coil should

show very low resistance if it is a series field coil.

The strength of the core of an electromagnet depends upon the material from which it is constructed and which of the following?

The number of turns of wire in the coil and the amount of current (amperes) passing through the coil.

A voltage regulator controls generator voltage by changing the

resistance of the generator field circuit.

The overvoltage control automatically protects the generator system when excessive voltage is present by

opening the shunt field circuit

When DC generators are operated in parallel to supply power for a single load, their controls include an equalizer circuit to assure that all generators share the load equally. The equalizer circuit operates by

increasing the output of the low generator and decreasing the output of the high generator until they are equal.

What is the maximum amount of time a circuit can be in operation and still be an intermittent duty circuit?

Two minutes

The most common method of regulating the voltage output of a compound DC generator is to vary the

current flowing through the shunt field coils

If any one generator in a 24-volt DC system shows low voltage, the most likely cause is

an out-of-adjustment voltage regulator

How can the direction of rotation of a DC electric motor be changed?

Reverse the electrical connections to either the field or armature windings.

Static inverters are electronic devices that change DC to AC with the

use of an oscillator

Aircraft which operate only AC generators (alternators) as a primary source of electrical power normally provide current suitable for battery charging through the use of

a stepdown transformer and a rectifier

During inspection of an anticollision light installation for condition and proper operation, it should be determined that

the anticollision light can be operated independently of the position lights

Major adjustments on equipment such as regulators, contactors, and inverters are best accomplished outside the airplane on test benches with necessary instruments and equipment. Adjustment procedure should be as outlined by

the equipment manufacturer.

A battery-generator system provides direct current. On installations requiring alternating current from the battery-generator system, it is necessary to have

an inverter.

An aircraft electrical circuit control relay is

an electronically operated switch